1. Field of the Invention
The present invention relates to a drill bit for drilling a hole in layered materials wherein the first layer encountered by the bit is softer than the second layer and wherein the second layer encountered by the bit produces chips capable of abrading the first layer.
2. Description of the Related Art
Using a drill bit of the prior art to drill a hole in layered material including a layer of relatively soft composite material and a layer of relatively hard metallic material has been unsatisfactory. The relatively hard metallic material produces chips which abrade the relatively soft composite material as they exit the hole. This abrasion causes the hole in the composite material to become bell-mouthed.
In an effort to overcome this problem, current manufacturing practice is to drill through the layers of composite and metallic materials using one or a series of undersized drill bits. The hole drilled is then brought to size by a final reaming operation. It is also known in the art to drill a hole with a full-size drill bit while using extremely high air and/or coolant pressure to rapidly remove the metallic chips before erosion takes place.
It is an object of the present invention to provide a drill bit for drilling layered material which utilizes a standard size drill bit and coolant pressures normally found in machine tools, i.e., in the range of 30 to 40 psi.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.